Exclusion Ring Alignment for Clean Wafer Edge Deposition
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Solution Overview
Problem
In chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes, particulate contamination from unwanted film deposition on the wafer edge and backside poses significant challenges, leading to defects and contamination during handling.
Innovation Solution
The use of an exclusion ring with a first alignment structure on its underside and a second alignment structure on the platen ensures proper alignment and prevents deposition on the wafer edge and backside by controlling the flow of deposition control gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the wafer edge and backside are unprotected during deposition, then the CVD material can be deposited on these surfaces, but this leads to peeling and flaking that introduces particulates into the chamber
Solution Approach 1:
An exclusion ring is introduced as an intermediary component between the wafer and the deposition environment. The ring creates a physical barrier and associated gas flow patterns that prevent CVD material from reaching the wafer edge and backside, thereby eliminating the source of particulate contamination while allowing uninterrupted deposition on the front surface
Solution Approach 2:
The solution segments the wafer protection approach by using an annular exclusion ring that specifically targets only the edge and backside regions. This segmented approach allows selective deposition control - protecting vulnerable areas from material accumulation while maintaining full deposition coverage on the functional front surface of the wafer
2Productivity
If the wafer backside is exposed during ALD, then film can be deposited through gaps accessing the backside, but this excess film is susceptible to flaking during wafer transport
Solution Approach 1:
The exclusion ring acts as a mediator that controls gas flow paths during ALD processing. By positioning the ring to overlap the wafer periphery, it creates a protective gas flow barrier that prevents reactive species from accessing the backside through gaps, thereby preventing unwanted film deposition on surfaces where adhesion is problematic
Solution Approach 2:
The solution adds a spatial dimension to the protection approach by using the exclusion ring's peripheral overlap configuration. This dimensional approach creates a three-dimensional gas flow control zone that extends beyond the wafer surface, effectively blocking deposition pathways to the backside while maintaining two-dimensional deposition uniformity on the front surface
3Object-affected harmful factors
If an exclusion ring is used to prevent deposition on wafer edge and backside, then particulate contamination is reduced, but proper alignment between the exclusion ring and wafer must be ensured
Solution Approach 1:
The alignment structures utilize asymmetric geometric features - such as triangular or trapezoidal guiding surfaces with specific angle ranges (30-60 degrees) - that create inherent directional guidance. This asymmetric design ensures that the exclusion ring self-aligns with the wafer in a single correct orientation, eliminating the need for complex active alignment mechanisms while guaranteeing proper positioning
Solution Approach 2:
The alignment system operates on a self-service principle where the geometric features of the exclusion ring and platen automatically guide proper alignment through mechanical interaction. The guiding surfaces and engagement features cause the ring to self-position correctly relative to the wafer during placement, without requiring external alignment tools or complex control systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively prevents unwanted deposition on the wafer edge and backside, reducing particulate contamination and ensuring uniform and defect-free film deposition on the wafer front side.
Implementation Method 1
Chemical vapor deposition ('CVD') is a gas reaction process commonly used in the semiconductor industry to form thin layers of material, known as films, over an integrated circuit substrate. The CVD process is based on the thermal, plasma, or thermal and plasma decomposition and reaction of selected gases.
Implementation Method 2
The first alignment structure includes guiding surfaces that increase the likelihood that the first alignment structure will receive and mate with the second alignment structure. Proper alignment and mating of the second alignment structure with the first alignment structure promotes alignment of the exclusion ring with the wafer to within process tolerances.
Data Source
AI summary
The present disclosure relates to exclusion rings for use in processing a semiconductor substrate in a processing chamber, such as a chemical vapor deposition chamber. The exclusion ring includes an alignment structure that cooperates with an alignment structure on a platen on which the exclusion ring will rest during processing of the wafer. The first alignment structure includes a guiding surface which promotes the reception of and positioning of the second alignment structure within the first alignment structure. Methods of utilizing the described exclusion rings are also described.